The present invention relates to a novel room temperature-curable organopolysiloxane composition or, more particularly, an organopolysiloxane composition capable of giving a highly oil resistant rubbery elastomer by curing at room temperature.
Needless to say, oil resistance of the material is one of the most important requirements for gaskets, packings and the like made of cork, an organic rubber, asbestos and the like when such parts are used in various machines or, in particular, as a sealing material around automobile engines. These conventional materials are not always satisfactory due to not only the insufficient sealing performance but also the inconvenience that they should be manufactured in a preshaped form adaptable to each part. Therefore, these conventional materials are under continuous replacement with so-called formed-in-place gaskets (FIPG) by use of a room temperature-curable silicone rubber to give great advantages in respect of the good workability, hermetic sealability and heat resistance. A problem recently encountered with such FIPG formed of an organopolysiloxane composition and used in automobiles, however, is the degradation of the cured silicone rubber in the course of long-term use at elevated temperatures to cause oil leakage which is also partly due to the trend that the gear oils used in the transmissions and the like of modern automobiles is a low-viscosity multigrade one with admixture of a large amount of an extreme-pressure additive in compliance with the requirement of reduced fuel consumption.